Digitally stored electronic maps are used to provide directions to users of mobile devices, for example, using any of a wide array of standalone map or direction application programs or apps. Today's electronic maps correctly determine where a mobile device is within a few feet or meters, or show where the user of that mobile device is on the electronic map in real time. Electronic maps also typically include other functionality, such as providing turn-by-turn directions to nearly any location. Additional elements such as traffic or wrecks may also be shown.
Electronic maps also appear in other applications aside from standalone mapping applications. For example, ride sharing applications, taxi applications, video games, and other applications may use digital maps. These or other applications obtain electronic maps by calling a map server computer through an Application Programming Interface (API). Thus, a single electronic map provider that owns or operates the server computer may supply the electronic maps for many different applications.
Electronic maps are constructed from a variety of different sources, with degrees of accuracy often depending on their intended application. For maps used to provide turn-by-turn directions on roadways, the accuracy of the roadway position within the electronic map is important to the functioning of the map, since inaccuracies will become very apparent to users as they attempt to navigate. However, collecting road position information to construct an electronic map is often a labor intensive process, and frequently achieved through manual collection of street data using a fleet of vehicles and other on-the-ground collection infrastructure. Furthermore, the ability of the electronic map to accurately project a user's real-world physical location onto a position in an electronic map is not guaranteed, since systematic errors in the Global Positioning System (GPS) collection data can lead to misalignment of sections of the map. Systematic errors in GPS collection data may arise from miscalibration of a collection vehicle's inertial measurement unit (IMU), a lack of satellite signal, signal obstruction, or multipath error. Furthermore, because roadways may change, for example, as the result of construction, the electronic map may not be accurate in an interim period before manual collection of street data is taken again. In general, conventional means of improving mapping accuracy involve updating the map with new on-the-ground data collection, requiring manual data collection to be taken and updated repeatedly. Improved ways of updating electronic maps, identifying changes to the roadway and improving the accuracy of the map are needed to provide more real-time updates without needing to manually re-take street data.